1. Field of the Invention
The present invention relates in general to magnetic arrays for use with periodic magnetic devices such as synchrotrons, free electron lasers, wigglers, undulators, and magnetic separators, and particularly to such arrays constructed with magnets which surround poles on substantially all available pole surfaces.
2. Description of Prior Developments
Synchrotrons are used to produce certain types of radiation, such as ultraviolet light and x-rays, by forcing a stream of electrons to follow a curved path. In order to increase the brightness and intensity of this radiation, the electrons are directed through a series of magnetic fields that alternate in polarity and that are perpendicular to the electrons' direction of travel. These magnetic fields cause the electrons to follow a sinusoidal path and thereby increase the intensity and brightness of the radiation produced in accordance with known practice.
The magnets which are used to produce these alternating magnetic fields are known as wiggler magnets or undulator magnets. The difference between wiggler magnets and undulator magnets is in the degree of angular deflection produced by their magnetic poles. The deflection angle of a wiggler array is much greater than the natural emission angle of synchrotron radiation while the angular deflection produced by each set of poles in an undulator magnet array is less than or comparable to the natural emission angle.
Such magnets are presently required to produce extremely high field strengths, often in excess of two Tesla (2.0 T). Prior wiggler and undulator magnet designs have employed rare earth permanent magnets spaced between steel pole pieces. Practical field strengths of 1.8 T have been achieved with these designs. However, all known prior hybrid wiggler and undulator designs apply magnet material to only two sides or faces of each pole.
In order to introduce direct flux into the remaining three pole faces not facing the gap through which the electron beam passes, prior designs have oversized the magnets to extend beyond or overhang the pole faces in contact with the magnet material. This resulted in the use of significantly large amounts of costly magnet material and required a relatively large envelope within which to mount the magnet arrays.
One particular magnet array suitable for use with synchrotrons is disclosed in U.S. Pat. No. 5,019,863 which is incorporated herein by reference. The magnet array disclosed in this patent requires the use of tapered or wedge-shaped pole pieces and permanent magnets in order to allow a greater volume of magnet material to be placed between the poles. Although this arrangement functions adequately for its intended purpose, it's design is not the most economical.
That is, wedge-shaped magnets and poles are typically machined from rectangular blocks thereby necessitating removal of costly raw materials and requiring significant time for machining and grinding. Moreover, this particular design requires a relatively long or tall pole height in order to achieve high magnetic field strengths as is customary with designs which apply magnets to only two faces of each pole.
Accordingly, a need exists for a magnetic array suitable for use with synchrotron wiggler and undulator devices and which is able to produce high magnetic field strengths while being economical to manufacture.
A further need exists for such a magnetic array which is compact in size so as to reduce the amount of costly magnetic material required to produce a given magnetic field strength.